The use charge paid for the use of a telephone can be charged in different ways. In connection with fixed networks the operator always knows the address of the subscriber. Then no great risks relate to the billing, as any unpaid telephone bills can be taken in execution from a person in possession of the subscription. Therefore the use charge of fixed telephone subscriptions is generally invoiced afterwards.
As cellular telephones become more general they present new challenges regarding the collection of subscribers' use charges. A successful collection is also important because a bill generated by a cellular telephone can become very high already in a short time, as the use charges per time unit are relatively high compared to the use charges in the fixed network. In addition a portable terminal is readily used more often than a fixed telephone subscription. Further, if the address information of a cellular telephone user is incomplete or out-of-date it can be inconvenient to collect the outstanding claims. Various prepaid subscriptions are generally used in order to solve the above problem. In these arrangements a cellular telephone's user pays in advance a certain fee to his/her network operator for the use of the telephone. The user may utilise his/her cellular phone only as long as there is a prepaid amount left. Such prepaid subscriptions are in some countries the most common way to buy a cellular telephone subscription.
One generally used way to realise a prepaid subscription is to use a disposable SIM card (Subscriber Identity Module). In this arrangement the SIM card may be used as long as there has been originally stored money/right of use in it. When the right of use expires it is thus necessary to acquire a new SIM card. The production and distribution of such disposable SIM cards represent extra costs to the network operator selling and distributing such SIM cards. Further, the user must remember to buy a new SIM card in good time in order to be able to replace the SIM card when the operating time of the previous SIM card expires.
Another common way to charge the advance payment is to add right of use to the SIM card via the serving cellular network. Then the terminal's user must have an account in a bank, a credit company or a company providing payment services. When the operating time of the SIM card is about to expire the terminal's user must establish a data transmission link to his/her credit company. If there is cover or credit on the user's account, then the amount defined by the user can be transferred to the account of the network operator during the data communication or after it. Then the network operator increases the balance/time of use by the corresponding amount in its own data system. However, this arrangement requires that the terminal's user has an account in some credit company which can be electrically utilised via the data network. Thus such users, which are located outside an electrical data network of this kind, are not able to utilise this approach.